Just a week after David Cameron cast one shadow over the human right to a fortnight abroad - asking Britons to worry about the carbon footprint of their holiday jets - his higher education spokesman, Boris Johnson, has identified another. After an attempt by a British Airways flight attendant to prevent him sitting next to his own children on a night flight, Boris has flushed out the admission that BA crew are encouraged to separate young passengers from potential paedophiles. Spotting a large bloke with an alarming laugh and barnet chatting to some of the half-fares, the airline employee had felt compelled to intervene. Perhaps the geezer seemed familiar and she mistakenly believed she had seen his face on Crimewatch rather than Question Time.

But, if it were not already enough that the Great British Holidaymaker might fall under suspicion of destroying the planet and interfering with young travellers, it also emerged this week that the act of ensuring that your papers are in order for a journey abroad will invite inspection of the possibility that the planetary vandal and potential pederast could also be a terrorist.

In the wake of new reports of the ease with which a fraudulent passport can be obtained, a squad of civil servants trained in scepticism will now quiz applicants for the little burgundy booklet with the Queen's face about whether they really are who they say they are. The aim is finally to close the scam, identified by Frederick Forsyth's The Day of the Jackal 36 years ago, in which it is possible to choose a new life for yourself from a graveyard.

Personally, having travelled with and without my children, I would think that nobody in their right mind would want to be placed next to anyone else's kids, and so BA's paranoia has its benefits. Boris, however, is clearly raising a libertarian principle, which can also be applied to the new passport procedures.

What we might call, for shorthand, the "Johnson" and "Jackal" rules are related. They are evidence of a culture of general suspicion. Years of fearing the worst - following high-profile news stories involving paedophile rings and terrorist attacks - have led to an official tendency to think the worst of everyone until otherwise proved. Because of documented cases in which such methods have been exploited, travelling children are protected from single men, and passport clerks from applicants who are vague about their origins.

As shown by Boris Johnson's anger this week - and the newspaper editorials warning that the new passport checks might lead to the creation of an "unprecedented database" of information about the public - the state's instinctive suspicion makes many instinctively suspicious of the state.

In fact, our society has become a perfect circle of doubt. A period in which the public's mistrust of authority is higher than almost ever before has now been followed by - or overlapped with - a spell in which authority's distrust of the public has reached unprecedented levels. "Who do you think you are?" sneer the voters to their leaders. "And who do you say you are?" comes the beady reply. "Trust no one" - the poster line for conspiracy thrillers - has now almost become a national anthem.

The paradox is that, while each side well knows why it distrusts the other, neither can understand why the other suspects it. But anger at falling under suspicion results from the human delusion that others see us as we see ourselves. The man who knows himself perfectly well to be a shaggy-haired, maverick paterfamilias and Latin-speaking member of the shadow cabinet jollying along his offspring before the cabin lights dim, cannot begin to understand why others fear that he might be inducting unaccompanied kids into some pervert's branch of the mile-high club.

Similarly, passport applicants who know perfectly well in their own heads that they are planning to read the new Ian Rankin on hot sand rather than to plot an attack on infidel western infrastructure cannot understand why their innocence is not immediately apparent to bureaucrats. Surely you don't have to have passed many civil service exams to see that they would be a very unlikely recruit to al-Qaida?

The only alternative to general suspicion, though, is targeted alarm. Young dark-skinned men would find it hardest to get passports; pale middle-aged men who still live with their mothers would be given the seats at the back of the plane, far away from the passengers making engine noises as they twirl their plastic replica jets through the air.

Such a system has been tried before: the stop-and-search law informally known as "sus" ("suspicion") was applied to black British citizens. But not only is such an approach morally suspect - because it demonises minorities and exposes them to prejudice - it is also questionable in practice because there will be terrorists and paedophiles who do not meet easy profiles. Indeed, one of the problems with the BA rules is that they don't go far enough, in assuming that there are no female paedophiles.

Such laws will never be fair or pleasant but, if a state imposes them, it's surely better that they apply to everyone. We have less to fear from a system that fears Boris Johnson as much as the next man.